A duck-type assistant method. For example, Active Support extends Date to define an acts_like_date? method, and
extends Time to define acts_like_time?. As a
result, we can do "x.acts_like?(:time)" and
"x.acts_like?(:date)" to do duck-type-safe comparisons, since
classes that we want to act like Time simply need
to define an acts_like_time? method.